The present invention relates to a vibration gyro having an H-shaped vibrator. More particularly, the invention relates to a vibration gyro having an H-shaped vibrator with high sensitivity and with minimal detection error.
A vibration gyro operates upon the principle that Corioli's force is generated when an angular velocity is applied to a body moving at a speed. That is, a velocity is given to the body by vibrating it, and Corioli's force, which is generated when an angular velocity is applied to the body thus vibrated, is detected as a displacement of the body, so that the angular velocity is detected.
In order to obtain a stable and accurate detecting voltage, it is necessary to suppress an error voltage generated by a detecting piezo-electric element due to a leakage of a driving voltage by a mechanical influence caused by a driving vibration of a vibrator and an electrical influence caused by a voltage which is applied to a driving piezo-electric element. On the other hand, the vibration gyro has recently been required to be small in size and lightened.
There has been known a conventional vibration gyro of a fork type as shown in FIG. 1. In the conventional vibration gyro, a fork-shaped vibrator 1 is provided with two vibrating members 4 each composed of a driving vibration plate 2 and a detecting vibration plate 3 disposed perpendicularly to the driving vibration plate 2. The vibrator 1 is supported at a lower end thereof by a supporting bar 5 extending vertically. A driving piezo-electric element 6 is mounted on each of the driving vibration plate 2 and a detecting piezo-electric element 7 is mounted on each of the detecting vibration plate 3, wherein polarities of which are arranged as shown in FIG. 1.
In the conventional vibration gyro, the driving vibration plate 2, that is a driving vibrating part of the vibrator 1 is separately and perpendicularly disposed to the detecting vibration plate 3, that is a detecting vibration part. Under such a structure, the driving vibration may not influence to the detecting piezo-electric element 7 and, therefore, a leakage of the driving voltage will be suppressed. However, since the supporting bar 5 does not support at a gravitational center of the vibrator 1, a noise vibration may be generated by the vibrator 1 thereby deteriorating a detecting accuracy of Corioli's force.
Further, the vibrator 1 may not easily be processed because the driving vibration plate 2 is unitary in form with and perpendicularly to the detecting vibration plate 3.
In the vibration gyro shown in FIG. 2, driving piezo-electric elements 12A and 12B are mounted on upper and lower portions, respectively, of both sides in a widthwise direction of a vibrator 11 and four detecting piezo-electric elements 13 are mounted on a side perpendicular to that in the widthwise direction. The upper driving piezo-electric elements 12A are opposite in polarity to the lower elements 12B. This vibration gyro also has a supporting bar 14 supporting the vibrator 11 and being secured to a casing 15. When a voltage is applied to the driving piezo-electric elements 12A and 12B, the vibrator 11 vibrates in a Y direction symmetrically in left and right directions and asymmetrically in upper and lower viewing from the front of the vibrator. Under this condition, the detecting piezo-electric elements 13 detect Corioli's force generating around an X direction which is perpendicular to the driving vibration direction.
On the other hand, in the vibration gyro shown in FIG. 3, the H-shaped vibrator 11 is supported by a plate spring 16 on which detecting piezo-electric elements 13A are mounted. In this vibration gyro, all the four driving piezo-electric elements 12A and 12B are equal in polarity with one another. In this vibration gyro, when a voltage is applied to the driving piezo-electric elements 12A and 12B, the vibrator 11 vibrates in the Y-direction symmetrically in left and right directions and in upper and lower directions viewing from the front. Under this condition, the detecting piezo-electric elements 13A detect Corioli's force generating around a Z direction by detecting a displacement of the plate spring 16.
According to the vibration gyro shown in FIG. 2, the driving piezo-electric elements 12A, 12B and the detecting piezo-electric elements 13 are commonly mounted on the vibrator 11 in proximity to one another. Therefore, there may occur a difficulty in that a large amount of leakage of the driving voltage from the driving piezo-electric elements 12A and 12B may be applied to the detecting piezo-electric element 13.
On the other hand, in the vibration gyro shown in FIG. 3 in which the displacement of the plate spring 16 is detected, a detecting accuracy may be influenced by a supporting system including the plate spring 16. In other words, the vibrator 11 may be influenced by the supporting system and the material of the casing. In order to prevent such a difficulty, the casing has to be formed of a heavy material so that the vibration gyro may not be made small in size and lightened.